Vapor deposition apparatus including pivoted shutters



y 7, 1968 a. BASS AN 3,381,660

VAPOR DEPOSITION APPARATUS INCLUDING PIVOIED SHUTTERS Filed June 9, 1967 United States Patent 3,381,660 VAPOR DEPOSITION APPARATUS INCLUDING PIVOTED SHUTTERS Benjamin Bassan, Framingham, Mass., assignor to National Research Corporation, Newton Highlands, Mass., a corporation of Massachusetts Filed June 9, 1967, Ser. No. 644,840 1 Claim. (Cl. 118--49) ABSTRACT OF THE DISCLOSURE A vacuum coating apparatus with a curving substrate holder, an elnogated source of coating vapors and a pair of pivoted shutters between substrate and source, all mounted in a vacuum chamber. The shutters protect the walls of the chamber from coating vapors in both open and closed positions and reflect heat back to the source in both positions and provide a gradual control of coating rate by movement between the two positions.

The present invention relates to vacuum coating apparatus of the type in which a rotary drum supports a substrate above a heated source of vapors in a vacuum chamber. In such apparatus it is necessary toprovide a shutter to prevent exposure of the substrate or supporting drum while the source is heating up or otherwise in between coating cycles.

It is the object of the present invention to provide an improvement in coating apparatus in which a shutter arrangement is used while provides rapid shutter control and also provides protection of the chamber from coating vapors, conserves heat at the source and provides ease of access to the coating source for maintenance and meets the foregoing criteria consistent with long times of exposure to a hot source of coating vapors over many coating cycles and economy of construction.

It is a further object of the invention to provide control over coating rate through the shutter mechanism without modification of evaporation rate or substrate speed.

The foregoing objects are accomplished by an apparatus as described generally in the foregoing abstract. The invention is now described specifically with reference to the accompanying drawing which is a partial sectional view of a preferred embodiment of the coating apparatus.

FIG. 1 is a partial front vertical section of the apparatus.

FIG. 1A is partial side vertical section of the apparatus.

Referring now to the drawings there is shown a coating source containing a charge of material to be evaporated. The coating source is preferrably an elongated trough or an elongated series of crucibles heated by a single turn induction coil, as described in U.S. Patent 2,935,589 to Baer and Steeves. The source is heated to project vapors upwardly as indicated by lines 11. Mounted above the source is a cylindrical drum 12, a portion of which is shown in cutaway form. Cooling coils 14 are connected to the drum. A substrate 16 to be coated, e.g. plastic film is moved along with the drum as it rotates in the direction 13. A shutter assembly 20 is located between the source and substrate to selectively cut off the passage of vapors from the source to substrate. This entire apparatus is enclosed in a vacuum chamber evacuated to 10" torr.

3,381,660 Patented May 7, 1968 In accord with the present invention, the shutter apparatus takes the improved form of a pair of gates 22. Each gate is pivoted about an axis 24 extending parallel to the direction of elongation of the source. Each gate is basically formed of a pair of legs-an upper leg 221 extending essentiaily transverse to the basic direction of evaporation and a lower leg 222 extending essentially parallel to the basic direction of evaporation. The pivot 24 is located on the lower half of leg 222.

The gates are arranged so that their outer ends are movable about the axis 24 along the circular paths 26 passing very close to the substrate over a long path length. This is accomplished by keeping the radius of curvature from the axis 24 to the end 28 of each gate about equal to the radius of the substrate on the drum and locating the pivots at a distance about equal to the radius R. The axes 24 are separated from each other by a distance D less than 2R and placed symmetrically on opposite sides of the source.

In operation the shutters 22 are initiallyin position I as the source 10 is warmed up. Then the shutters are moved to position II and drum 12 is rotated as indicated by arrow 13 to move a substrate 16 to intercept the coating vapors 11. The shutters afford a very rapid response because of their split pivotal construction and short angle of pivoting (about 30-60 degrees). The position of either or both shutters can be adjusted between I and II to control coating rate since the paths 26 of the shutter ends is close to the substrate 16 for a substantial portion of its curving path. The shutter arrangement also ensures excellent protection of the vacuum chamber walls from vapors which limits the necessity for chamber cleaning between coater runs. The excellent reflectivity of the shutters (which themselves become coated with a shiny deposit) reflects heat back to the source very well because the geometry of the shutters has their inner coated surface looking at the source top in positions I and II and all positions in-between.

Deposits on the shutter tend to flake and fall ofi in portions. But the arrangement shown prevents these flakes from falling into or on the source 10 to cause coating instability or short circuiting the source heater.

Between coating cycles one or both shutters can be turned to a position indicated at III for access to the source 10 from the sides.

Another substantial benefit of this construction is flexibilitythe source can be raised or lowered for different coating jobs without disturbing the drum 12 or shutters 22.

FIGURE 1A shows a side view of the apparatus indicating fixed end shields 23 located just far enough from movable shields 22 to allow operation of shields 23 without jamming (about inch typically). Movable shields 22 and fixed shields 23 are all water cooled.

What is claimed is:

1. In a vacuum coating apparatus comprising a cylindrical substrate support, a substrate mounted on the support with a radius of curvature R, a vapor source located below the support, and a shutter apparatus, the improvement wherein said shutter apparatus comprises a pair of similar pivoted gates disposed symmetrically about the source and being constructed and arranged to pivot between a first position wherein gate ends meet so that the gates block the vapor path between source and substrate and a second position wherein the gate ends are spread to clear said path, the gates being constructed so that said gate ends have a radius of curvature about their pivot axes substantially equal to R, the pivot axes of said gates extending essentially parallel to the axial direction of said cylindrical support and being disposed symmetrically on opposite sides of said source and spread at a distance less than 2R from each other and each being located at a distance from the substrate substantially equal to R, each of said gates having a two leg construction with an upper leg exending transverse to said evaporation direction and a lower leg extending parallel to said evaporation direction, the pivot axis being located along the lower half of said lower leg.

References Cited UNITED STATES PATENTS Allen 239-503 X Fitzsimons 239-507 Logerot et al. 239-515 X Ross 118--49 Smith 2395 11 X Chilowsky 118-49 X MORRIS KAPLAN, Primary Examiner. 

